He Jun Ling, 32, was sentenced to seven weeks' jail due to greater culpability while Gao Yue Qiang, 32, Liu Xiangying, 33, and Wang Xian Jie, 39, were sentenced to six weeks' jail each, reported the Channel News Asia.
The four men pleaded guilty today, after their lawyers said last Friday that their clients' decision to plead came after prosecution gave an indication of the various sentencing options.
Senior District Judge See Kee Oon while giving his grounds for decision said the public transport was an essential service and that although the four men's conduct was motivated by their grievances, their plea of guilt indicated that they knew they ought not to have taken the law into their own hands.
He said the move had the potential to affect the daily lives of all who relied on public transport in the city state.
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The striking drivers also chatted online and made personal visits to fellow bus drivers from China who were employed by the bus company.
Judge See noted the defence lawyers' points that the key in the case was the failure on the part of the four to submit the notice before going on strike.
But he said "ignorance of the law cannot excuse them entirely".
The four were accused of inciting and participating in the illegal strike on November 26 last year, when 171 bus drivers failed to report for duty in a protest over pay and living conditions.
According to local media reports, they were all from China hired as drives by the leading local public transportation company Singapore Mass Rapid Transport (SMRT).
Strike is illegal under Singapore's laws against industrial unrest and the last strike here took place at a shipyard in 1986.